Yurii P. Sinichkin

In Vivo Fluorescence Spectroscopy of the Human Skin: Experiments and Models

The results of the experimental investigation of autofluorescence spectra of human skin in vivo caused by the UV radiation of the skin and by the external mechanical pressure applied to the skin are presented. These results are compared with results of Monte Carlo modeling of the autofluorescence of the skin with variable blood content. The proposed simple model of the skin gives the possibility of evaluation of changes of the blood and melanin content within the skin.

In-vivo and in-vitro study of control of rat skin optical properties by action of osmotical liquid

We present experimental results on optical properties of the rat skin controlled by administration of osmotically active chemical, such as glycerol. In vivo reflectance and in vitro reflectance and transmittance spectra of the rat skin were measured. Results of experimental study of influence of glycerol on reflectance spectra of the rat skin are presented. The significant increase of transmittance and decrease of reflectance of the rat skin under action of osmotical agent are demonstrated. Basing on mathematical modeling the optical parameters of the rat skin are determined.

Human sclera dynamic spectra: in-vitro and in-vivo measurements

Experimental results on the optical properties of the human eye sclera controlled by administration of osmotically active chemicals, such as propylene glycol and glucose are presented. Administration of chemical agents induces diffusion of matter and as a result equalization of the refractive indices of collagen and ground material. Experimental study of influence of propylene glycol and glucose on reflectance and transmittance spectra of human eye sclera was performed. In vitro diffusion reflectance spectra of the whole human eye and transmittance spectra of the sclera samples were investigated. In vivo measurements were fulfilled on a rabbit eyes. The significant increase of transmittance and decrease of reflectance of human eye sclera and rabbit eye under action of osmolytic liquids was demonstrated. The matter diffusion coefficient for the scleral samples impregnated by glucose solution was estimated; the average value is 1.27x10-5 ± 2.26x10-6 cm2/sec. The results are general and can be used to describe many other fibrous tissues.

In-vivo and in-vitro study of control of rat skin optical properties by action of 40%-glucose solution

We present experimental results on optical properties of the rat skin controlled by administration of osmotically active chemical, such as the 40%-glucose solution. In vivo reflectance and in vitro transmittance spectra of the rat skin were measured. Result of the experimental study of influence of the 40%-glucose solution on reflectance and transmittance spectra of the rat skin are presented. The significant increase of transmittance and decrease of reflectance of the rat skin under action of osmotical agent are demonstrated. The average value of glucose solution diffusion coefficient was estimated as 1.101(DOT)10-6+/- 0.153(DOT)10-6 cm2/sec.

Influence of glycerol on the transport of light in the skin

We present experimental results on optical properties of the rat skin controlled by administration of osmotic chemical, such as glycerol. Administration of glycerol induces matter diffusion and as a result equalization of the refractive indices of skin scatterers and interstitial fluid. The significant increase of the skin sample transmittance under action of glycerol has been demonstrated. The mean value of the glycerol diffusion coefficient has been estimated as(formula available in paper).

Estimation of glucose diffusion coefficient in scleral tissue

Results of experimental and theoretical study of the optical properties of the eye sclera controlled by administration of osmotically active chemical, such as glucose, are presented. Glucose administration induces the diffusion of matter and as a result the equalization of the refractive indices of collagen fibrils and base material, and corresponding changes of transmittance spectra of scleral tissue. Transmittance spectra of the human scleral samples impregnated by glucose were measured. The significant increase of transmittance under action of osmotic liquid was observed. The diffusion coefficient of glucose within scleral tissue was estimated; the average value is 3.45 X 10-6 +/- 4.59 X 10-7 cm2/sec. The results are general and can be used to describe many other fibrous tissues impregnated by osmotically active chemical agents.

Fluorescence spectroscopy of human skin

The advantages of optical spectroscopy in skin are discussed. The basis for fluorescence spectroscopy is briefly presented. The potential for in vitro and in vivo fluorescence spectroscopy of biotissues is significant, but not yet well developed. With the help of fluorescence spectroscopy and layer-by-layer skin surface strippings technique the important knowledge for autofluorescence spectra from different skin layers have been obtained. Resolution of autofluorescence spectra into discrete excitation-emission bands is presented, related to various skin fluorophores.

Diffusion of glucose solution through fibrous tissues: in-vitro optical and weight measurements

The diffusion of glucose with various concentrations through human sclera and cerebral membrane in vitro was studied. The dynamics of this process was monitored by time-dependent weight and optical measurements. Glucose administration induces the diffusion of matter and as a reslut the equalization of the refractive indices of collagen fibrils and ground material, and corresponding changes of transmittance spectra of fibrous tissue. Transmittance spectra of the human scleral and cerebral membrane samples impregnated by glucose were measured. Investigation of diffusion process in scleral samples, previously dried and swelled in distillated water was performed. Experimental results are presented.

Fluorescence spectroscopy in combination with reflectance measurements in human skin examination: what for and how

Reflectance and fluorescence spectroscopy are successfully used for skin disease diagnostics. Human skin optical parameters are defined by its turbid, scattering properties with nonuniform absorption and fluorescence chromophores distribution, its multilayered structure, and variability under different physiological and pathological conditions. Theoretical modeling of light propagation in skin could improve the understanding of these conditions and may be useful in the interpretation of in vivo reflectance and autofluorescence spectra. In the present work the temporal behavior of in vivo reflectance and autofluorescence (excitation wavelength 337 nm) spectra of human skin under ultraviolet irradiation and external mechanical pressure were investigated. Experimental results and Monte Carlo modeling of light distribution in skin were compared and demonstrated good agreements. Combination of diffuse reflectance and autofluorescence measurements is a very promising technique for precise erythema and pigmentation of the human skin evaluation.

In-vitro study of control of human dura mater optical properties by acting of osmotical liquids

We present experimental results and computer modeling of investigation on the optical properties of the human dura mater controlled by administration of osmotically active chemical, such as mannitol and glucose solutions with various concentrations. Administration of chemical agent induces diffusion of matter and as a result equalization of the refractive indices of collagen and ground material. Results of experimental study of influence of osmotical liquids (mannitol and glucose solutions) on reflectance and transmittance spectra of the human dura mater are presented. The significant decreasing of the reflectance and increasing of the transmittance of the human dura mater samples under action of osmotical solutions were demonstrated.